​“Am I stoned?” There’s an app for that

As the prevalence of cannabis use increases, there is growing concern about users who drive while under the influence of cannabis. A mobile app that reliably and specifically detects cannabis-induced impairments could potentially serve as a roadside sobriety test, similar to breathalyzer and field tests for alcohol. However, developing such a test is very challenging.

“The whole idea of having a field sobriety test for cannabis use is complicated,” said Harriet de Wit, PhD, professor in the Department of Psychiatry and Behavioral Neuroscience at the University of Chicago. Unlike with alcohol, “we don’t yet have a biochemical measure [for cannabis]...so the next idea might be using a performance measure.”

Walking in a straight line and reciting the alphabet backwards are examples of performance measures typically used to assess alcohol intoxication, but assessing cannabis-induced impairments in a real-world setting is much more difficult. In fact, the performance measures used for alcohol are not sensitive to cannabis.

de Wit and a doctoral student in her laboratory, Elisa Pabon, developed a prototype app called “Am I Stoned” to help cannabis users understand their level of impairment. They recently completed a clinical research study to test the app’s accuracy in detecting whether or not someone is under the influence of delta-9 tetrahydrocannbinol (THC), the main psychoactive ingredient of cannabis.

“[The] majority of the U.S. has already legalized medicinal cannabis for nerve pain, PTSD, etc., and nine states [and the District of Columbia] have legalized recreational, adult use of marijuana. This is why it’s important to conduct research studying its effects, particularly [its] cognitive and behavioral effects,” Pabon said.

Pabon presented her research findings at the April 2018 meeting of the American Society for Pharmacology and Experimental Therapeutics in California. The research was funded by an award from the National Institute on Drug Abuse, which is interested in finding ways to use mobile technology in substance abuse research.

Twenty-four non-daily cannabis users received a capsule containing placebo or one of two doses of THC, 7.5 or 15 mg, before completing four behavioral tasks both on a computer and an iPhone. The tasks measured cognitive processing speed, reaction time, fine motor coordination, and working and spatial memory.

THC impaired the participants’ performance on 3 of the computer-based tasks, but only on one of the iPhone tasks. Pabon and de Wit concluded that the iPhone tasks may have been too brief to detect drug effects.

A test of tapping speed helps app users assess their level of impairment from marijuana use.

The effect of THC on performance was not dose-related on either the computer tasks or the iPhone task, meaning that THC produced similar levels of impairments at both the 7.5 mg and 15 mg doses. The 7.5 and 15 mg doses of THC were chosen because they fall within the range typically achieved by recreational cannabis users.

The participants were also asked to rate their level of impairment and experience of drug effects. In general, after unknowingly receiving THC, participants were aware of their impairments on task performance and reported feeling high for at least 4 hours.

In general, THC-induced impairments are mild, difficult to quantify, and vary considerably among individuals. Because of these issues, de Wit explains that the app was designed “as an aid for personal use,” rather than as a field sobriety test for cannabis. Users could perform the tasks a few times while sober to generate a personal baseline, then again after using cannabis. The app could then tell users if they are impaired relative to their sober performance.

Pabon and de Wit are motivated to continue development and testing of their “Am I stoned?” app, with hopes of eventually releasing it for public use. The next step is to “take what we learned from this pilot study and apply it to the optimization of our app - to get it to be more sensitive to THC-induced impairments,” Pabon said. She plans to continue researching the effects of THC and cannabis, particularly investigating which factors may influence an individual’s response to cannabis.

Ashley Vena

Ashley Vena, PhD, is a second-year postdoctoral fellow in the Department of Psychiatry and Behavioral Neuroscience at the University of Chicago. She conducts research on substance use disorders in the Clinical Addictions Research Laboratory.